When a reaction system is at equilibrium: a. there is no more chemistry happening. b. the amounts of reactants and products are exactly equal. c. the reaction rate in the forward direction is at a maximum. d. the reaction rate in the reverse direction is at a minimum. e. the rates of the reaction in the forward and reverse directions are exactly equal.

Option (e) is the correct answer.

Explanation:

Equilibrium is defined as the state of a chemical reaction in which the rate of forward reaction is equal to the rate of backward reaction.

The state of equilibrium is represented by a double sided arrow as "" in a chemical equation.

For example,

Therefore, we can conclude that when a reaction system is at equilibrium then the rates of the reaction in the forward and reverse directions are exactly equal.

1. the question asks the most appropriate, which seems to rule out "all of the above." your choice appears to be the correct one.

2. the protocol described is good for identifying correlation, but not cause and effect. for cause/effect, you need to devise a protocol that will assign the treatment (or not) to groups that have essentially the same "demographics" with respect to all the other variables. your choice regarding control group seems appropriate. random assignment of treatment (choice d) may be appropriate also. (i think you can argue that b and d are just different descriptions of the same method.)

3. d will randomize the birds, but may not guarantee there are 10 in each group. e will do both, so seems the better choice.

comment on question 2

based on the problem statement, it seems clear that confident, attentive drivers are more likely to use daytime running lights. so, the protocol might need to be devised in such a way that the lights would be turned on or off without the driver's knowledge. (an attentive driver will figure it out.) assigning a confident, attentive driver to a group required to drive without running lights might mess with his/her confidence and attentiveness. you don't want your experiment to do that. (nor do you want the experiment to subject a driver to greater risk of accident as a consequence of driving without running lights.) experiments involving human safety are always problematic.